Relationships between days after insemination and changes in mass, inner layer length, and outer and inner layer widths of egg sacs associated with the absorption of water were examined in Hynobius nigrescens. Egg sac mass, which exhibited a continuous increase irrespective of water temperature until hatching, was the best parameter for estimating dates of oviposition. A regression equation for this purpose is presented by applying the analysis of analogue and digital data.

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Specimens of the mamushi (genus Agkistrodon) from Tsushima Island were examined and compared with congeners from the mainland of Japan, China, and South Korea. The Tsushima specimens collectively differed from these congeners in several characters, and thus are described as a new species, A. tsushimaensis. A brief taxonomic key to the Agkistrodon blomhoffii complex is also provided.

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A female R. rugosa was found to spawn more than once in one breeding season. This was confirmed over two years, and is the first observation of multiple spawning by this species ascertained in the field.

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